Dredge cutterheads are generally conical with a multiplicity of hard rock cutting teeth or replaceable edges projecting outwardly from helical support vanes or blades disposed about the conical surface of the cutterhead. The cutterhead normally has a hub which fits around a shaft that provides the torque for turning the cutterhead in its operation of dredging the bottom of waterways. The cutterhead encounters all kinds of material, including rock, which must be removed.
For the purpose of digging in rocky ground the cutterhead is fitted with teeth of high hardness and high impact properties. for the purpose of digging in soft to medium-soft ground the cutterhead is provided with edges of moderate hardness welded to the leading edge of the cutterhead blades. The service life of such welded edges is not as long as that of the hard teeth of the rock cutterhead. The hard teeth extend radially a substantial distance ahead of the blade and do not perform efficiently in the soft-to-medium earth. Accordingly, it is highly desirable to provide a cutterhead employing teeth of high hardness and wear resistance arranged in such a manner as to be efficient for digging in soft-to-medium soils and also to provide the advantages of an easily replaceable forward edge.
The most common variety of replaceable tooth for a dredge cutterhead embodies a pyramidal shape which is attached by an adapter to the cutterhead blade in a manner such that the point of the pyramid is directed at the surface which is to be cut and the longitudinal axis of the tooth, generally passes through the centroid of the cutter blade section and is generally at an angle with respect to the profile plane of the cutterhead from the point of the pyramidal tooth so as to provide an efficient transmission of power to the tooth with a minimum of breaking force.
Replaceable edge cutterheads have been known in the prior art for use in soft-to-medium soils. Such cutterheads have the same basic structure of a conical or semi-spherical shape of helical blades or vanes, but they do not have individual teeth attached thereto or in rock cutterheads. The forward portions of the blades are covered with 2 or 3 large hardened, serrated sections welded end-to-end along the forward portion of the blade to provide an edge which, when worn, can be replaced by new edge sections rather than replacing the entire cutterhead. Wear of the cutting edge is fast and it is important to provide some method of renewing the cutting edge relatively quickly so as to be able to finish a job in a reasonable time and not incur the devastating expenses of delays. Accordingly, it has been important to find a means of making a cutterhead that can perform its dredging tasks properly, efficiently, and with a minimum of delays. Generally, it is believed that this end can be achieved by employing a cutterhead with replaceable teeth attached to the cutter blades in such a fashion as to dig through soft-to-medium soils with a minimum of power usage, a minimum of breakage and wear of the teeth, and a minimum of delays to replace broken or worn parts.
It is an object of this invention to provide an improved dredge cutterhead tooth assembly with a novel locking system. It is another object of this invention to provide an improved dredge cutterhead tooth assembly which will dig in soft-to-medium soils with less power usage and less wear of the cutterhead and its component parts than has been the case with previous systems. It is still another object to provide such a tooth assembly that is universal in that a single shape can be affixed to any location on the cutterhead rather than have a plurality of unique shapes, each being suitable for only one location. It is still another object to provide a tooth assembly system which will form a protective leading helical edge on the blades of a cutterhead. Other objects will become apparent from the more detailed description which follows.